Yeah, it's bracket racing. They have one in April, May, June, July, August, and two in September, always on Friday nights. The CSP events are pretty packed; usually 300 cars or so....maybe a few less early in the season. If you hot lap, you can get 7 or 8 runs in.
I think they do sell nitrous at the track, but I have no idea how much it is, or of it's competitively priced. You might want to check at ColoradoStangs.com, some of the guys on there run nitrous.